I'm kinda that way in nearly every material aspect; I have had 9 computers (6 Macs, 3 PCs) in the last 1.5 years. Three cars in that time period as well. .
Holy crap. You are a compulsive buyer. Not sure if your "urge" to jump ship is anything like anyone elses urge.
I have not had any inkling of switching to another phone, another carrier definitely, but the iPhone is the apex of smartphones. I know there is nothing better and therefore don't bother thinking about finding another.